CN115659865A - Branched river section Manning roughness coefficient characterization method and resistance coefficient calculation method based on same - Google Patents
Branched river section Manning roughness coefficient characterization method and resistance coefficient calculation method based on same Download PDFInfo
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Abstract
The invention provides a branched river segment Mannich roughness coefficient characterization method and a resistance coefficient calculation method based on the same. Selecting a Freund number to reflect the water flow strength; selecting relative water depth to reflect the bed surface roughness; selecting a cross section river facies coefficient to reflect the cross section form; taking the ratio of the water passing area of the branched section to the water passing area of the single section at the upstream as a parameter reflecting the degree of contraction and expansion of the branched section; and constructing an empirical formula of the coefficient of the Manning roughness of the branched river reach. The empirical formula of the branched river channel Manning roughness coefficient can better reflect the comprehensive effect of different influence factors on branched river channel resistance, and the calculation accuracy is higher. The Manning roughness coefficient empirical formula is applied to the mathematical model of the branched river section, roughness values of different terrain boundaries and different flow rates can be accurately determined, the defect that the roughness cannot be automatically adjusted according to river bed erosion and water flow condition changes in the past mathematical model can be well overcome, and the simulation precision of the mathematical model is improved.
Description
Technical Field
The invention relates to the technical field of water conservancy and water transport engineering, in particular to a branched river segment Mannich roughness coefficient characterization method and a resistance coefficient calculation method based on the same.
Background
The river channel resistance determines the loss of mechanical energy of water flow in the movement process, is closely related to water flow turbulence and sediment movement, is a basic problem of river dynamics research, and is also an important foundation for river numerical simulation. The predecessors mainly developed a lot of research from two aspects of the formation and calculation of river channel resistance. According to the different sources of the friction resistance, the resistance of the alluvial river can be divided into the riverbed resistance, the riverbank and shoal surface resistance, the canal form resistance (also called river resistance), the artificial building resistance and the like. The existing moving bed resistance calculation methods include a resistance segmentation method and a comprehensive resistance method. In the past, few people propose corresponding resistance calculation formulas for different river types, the research related to the movable bed resistance calculation of the branched river section is few, and the difference and the similarity between the branched river section resistance distribution and other river sections are not separately considered even if the observation data of the branched river section are available. Generally speaking, the existing moving bed resistance calculation formula has poor adaptability in branch river sections.
Disclosure of Invention
The invention provides a branched river segment Manning roughness coefficient characterization method and a resistance coefficient calculation method based on the same, and aims to solve the problems that an existing typical moving bed resistance formula reflects the branched river segment resistance change rule, and the degree and the calculation accuracy are poor. The branched river section resistance coefficient calculation formula provided by the invention is established based on the consideration of main influence factors of the branched river section resistance, namely, water flow strength, bed surface roughness, cross section morphology and branched section shrinkage and expansion degree.
In order to solve the technical problems, the invention adopts the following technical scheme:
a branched river segment Mannich roughness coefficient characterization method comprises the following steps:
s1, selecting a Freund number Fr to reflect the water flow strength;
s2, selecting relative water depth to reflect the roughness of the bed surface;
s3, selecting a section river phase coefficient to reflect the cross section form;
s4, aiming at the influence of the contraction and expansion of the section of the branch section on the resistance, the water passing area A of the section of the branch section and the water passing area A of the single section of the upstream are used 0 The ratio is used as a parameter for reflecting the reduction and expansion degree of the section of the branch section;
s5, establishing an empirical relation between n and Fr, wherein n is a Mannich roughness coefficient;
step S6, further adding factors reflecting the roughness of the bed surface, the cross section shape and the sectional shrinkage and expansion degree of the branched section on the basis of the empirical relation of n-Fr in the step S5, and constructing a general type of a branched section mangning coefficient calculation formula
Wherein a, b, c, D and e are empirical coefficients, wherein H is the average depth of section, and D 50 Is the median diameter of bed sand, epsilon is the cross-section river phase coefficient, A is the water passing area of the branch section, A 0 The water passing area of the upstream single section is obtained;
and S7, substituting the prototype observation data into the formula, and calibrating to obtain empirical coefficients a, b, c, d and e, thereby finally obtaining the Manning roughness coefficient empirical formula.
Further, in step S2, the expression of relative water depth is H/D 50 The more H/D50Large indicates that the roughness of the bed surface is smaller.
Further, in step S3, a cross-sectional river facies coefficient ∈ = B is selected 1/2 H, river phase coefficient epsilon' = B substituted into maximum water depth of cross section 1/2 /h max And H/H max Three parameters are analyzed to be related to n, and three cross section shape parameters have certain influence on n along with epsilon, epsilon' and H/H max In the three morphological parameters, the correlation between epsilon and n is the best, the correlation between epsilon' is the second order, the relation between n and H/hmax is relatively scattered, and the correlation is the worst, so that the cross-sectional river facies coefficient is selected to reflect the cross-sectional morphology.
Further, in the step S4, the water passing area a of the branched section and the water passing area a of the single section of the upstream section are divided 0 The ratio is expressed as A/A 0 。
Further, in the step S5, the Mannich coefficient n and Fr have a better power function relationship,
the basic form of the relation from n to Fr is proposed by taking n as a dependent variable and Fr as an independent variable:
n＝aFr b 。
the invention also provides a branched river section resistance coefficient calculation method based on the Manning roughness coefficient, which is characterized by comprising the following steps of: the method comprises the following steps:
step I, according to the branched river reach Manning roughness coefficient characterization method of any one of claims 1 to 5, calculating to obtain an empirical formula of the research river reach Manning roughness coefficient;
and II, calculating according to an empirical formula of the Manning roughness coefficient to obtain the integrated resistance coefficient of the branched river section.
Further, in the step II, the Mannich roughness coefficient is substituted into the step II
Calculating a drag coefficient λ, where U represents the average flow velocity, U * The friction flow rate, the metabolic coefficient, the gravitational acceleration and the hydraulic radius are shown in the specification.
Compared with the prior art, the method has the following beneficial effects:
1. compared with the existing moving bed resistance coefficient formula, the comprehensive resistance coefficient calculation formula in the application has the advantages that the adaptability of the branch river section is improved, and the calculation accuracy is high.
2. The Manning roughness coefficient empirical formula in the application is applied to the mathematical model to calculate the roughness, the capability of automatically adjusting the roughness value according to riverbed erosion and deposition adjustment and inlet flow change is realized, and compared with the traditional method for determining the inverse roughness through actually measured data rate, the simulation precision of the mathematical model is improved.
Drawings
FIG. 1 is a graph showing the relationship between the measured value of the Mannich roughness coefficient n and the Freund number Fr in the embodiment of the present invention;
FIG. 2 is a diagram showing measured values of the Mannich roughness coefficient n and the relative water depth H/D according to the embodiment of the present invention 50 The relationship of (1);
FIG. 3 is a diagram showing the relationship between the measured value of the Mannich roughness coefficient n and the cross-sectional profile parameter ε, wherein ε = B 1 /2 /H；
FIG. 4 is a graph showing the relationship between the measured value of the Mannich coefficient n and the cross-sectional shape parameter ε ', in which ε' = B 1/2 /h max ；
FIG. 5 shows the measured value of the Mannich roughness coefficient n and the cross-sectional profile parameter H/H according to the embodiment of the present invention max The relationship of (1);
FIG. 6 is a graph showing the relationship between the measured value of the Mannich roughness coefficient n and the cross-sectional profile parameter ε at the same flow rate in the embodiment of the present invention;
FIG. 7 shows the measured value of the Mannich roughness coefficient n and A/A under the same flow rate in the embodiment of the present invention 0 Wherein A is the water passing area of the branched section, A 0 The water passing area of the upstream single section is adopted;
FIG. 8 is a comparison of the calculated value of the resistance coefficient obtained from the empirical relationship of n to Fr in the example of the present invention with the measured value;
fig. 9 is a comparison between the calculated value of the resistance coefficient and the measured value of the empirical formula of the integrated resistance coefficient of the branch river section according to the embodiment of the present invention;
fig. 10 is a comparison between a calculated value of the resistance coefficient obtained by a branch river reach comprehensive resistance coefficient formula and an actual measured value in a single section according to an embodiment of the present invention;
fig. 11 is a comparison between a calculated value of the resistance coefficient obtained from a formula of the combined resistance coefficient of the branch section according to the embodiment of the present invention and an actual measurement value;
FIG. 12 is a schematic view of the river situation and related calculation parameters of the Taigou waterway according to the embodiment of the present invention, wherein 5m is 5m above the navigation datum, 0m is the navigation datum, and 3 m and 5m are 3 m and 5m below the navigation datum respectively;
FIG. 13 is a schematic diagram of the computational meshing of a mathematical model of a level channel in accordance with an embodiment of the present invention;
FIG. 14 is a block diagram of a resistance equation method roughness determination routine in accordance with an embodiment of the present invention;
FIG. 15 is a comparison of the roughness calculation results determined by the resistance formula method according to the embodiment of the present invention with the measured values;
FIG. 16 is a comparison of the calculation results of the water line according to the embodiment of the present invention.
Detailed Description
The technical scheme of the invention is explained in detail in the following by combining the attached drawings, the embodiment and the comparative example.
Examples
A branched river section Manning roughness coefficient characterization method comprises the following steps:
s1, selecting a Freund number Fr to reflect the water flow strength;
s2, selecting relative water depth to reflect the roughness of the bed surface;
s3, selecting a section river phase coefficient to reflect the cross section form;
s4, aiming at the influence of the contraction and expansion of the section of the branch section on the resistance, the water passing area A of the section of the branch section and the water passing area A of the single section of the upstream are used 0 The ratio is used as a parameter reflecting the degree of contraction and expansion of the section of the branched section;
s5, establishing an empirical relation between n and Fr, wherein n is a Manning roughness coefficient;
step S6, further adding factors reflecting the roughness of the bed surface, the cross section shape and the sectional shrinkage and expansion degree of the branched section on the basis of the empirical relation of n-Fr in the step S4, and constructing a general type of a branched section mangning coefficient calculation formula
Wherein a, b, c, D and e are empirical coefficients, wherein H is the average depth of section, and D 50 Is the median diameter of bed sand, epsilon is the cross-section river phase coefficient, A is the water passing area of the branch section, A 0 The water passing area of the upstream single section is obtained;
and S7, substituting the prototype observation data into the formula, and calibrating to obtain empirical coefficients a, b, c, d and e, thereby finally obtaining the Manning roughness coefficient empirical formula.
The invention also provides a method for calculating the branch river section comprehensive resistance coefficient based on the Manning roughness coefficient, which is characterized by comprising the following steps of: the method comprises the following steps:
step I, according to the branched river reach Manning roughness coefficient characterization method of any one of claims 1 to 5, calculating to obtain an empirical formula of the research river reach Manning roughness coefficient;
and II, calculating according to an empirical formula of the Manning roughness coefficient to obtain the comprehensive resistance coefficient of the branch river section.
Further, in the step II, the Mannich roughness coefficient is substituted into the step II
Calculating a drag coefficient λ, where U represents the average flow velocity, U * The friction flow rate, the metabolic coefficient, the gravitational acceleration and the hydraulic radius are shown in the specification.
In the present embodiment, as shown in fig. 1, the manning roughness coefficient n and Fr have a good power function relationship, n decreases with the increase of Fr, and when Fr is larger than a certain value, the variation of n with Fr tends to be gentle. As shown in FIG. 2, although n and H/D 50 The point groups in the graph are distributed more dispersedly, but it can be seen that no matter the cross section is single or branched, n follows H/D 50 The increase of the bed surface tends to be reduced, namely, the smaller the roughness of the bed surface, the less the water flow is blockedThe smaller the force. As shown in fig. 3-5, the cross-section river facies coefficient epsilon = B is selected 1/2 H, river phase coefficient epsilon' = B substituted into maximum water depth of section 1/2 /h max And H/H max And analyzing the relation of the three parameters and n. The three cross-sectional morphological parameters all have some degree of influence on n. With ε, ε' and H/H max N tends to decrease, i.e., the wide and shallow branched sections have smaller resistance than the narrow and deep branched sections. However, of the three morphological parameters, ε is most closely related to n, ε' is second, n is related to H/H max The relationship of (2) is relatively random, and the correlation is the worst. In addition, because epsilon changes under different flow rates of the same section, in order to eliminate the influence of the flow rate, the change situation of n along with epsilon under the same flow rate is plotted, and the trend that n decreases along with the increase of epsilon can be still seen. As shown in fig. 6, the relationship between the measured value of the manning roughness coefficient n and the cross section shape parameter epsilon under the same flow rate in different river reach is shown.
As shown in fig. 7, for the influence of the contraction and expansion of the section of the branch section on the resistance, the water passing area a of the branch section and the water passing area a of the single section of the upstream section are used 0 Ratio of A/A 0 As a parameter reflecting the degree of reduction and expansion of the section of the branched section. The drag coefficient increases rapidly with increasing section reduction coefficient. In the branch channels (e.g. the branch channel) with larger cross-sectional area increase, A/A 0 And the water flow is rapidly dispersed, the turbulence is strong, the local loss ratio is increased, and the n value can reach 0.05. When A/A 0 When the value of n is equal to 1, the value of n is minimum, the section has no change of sudden shrinkage or sudden expansion along the way, the local loss is obviously reduced, and the resistance coefficient is smaller.
In the embodiment of the invention, a basic form of a relation from n to Fr is provided by taking n as a dependent variable and Fr as an independent variable:
n＝aFr b
wherein a and b are empirical coefficients obtained by actual measurement data calibration.
Based on 327 sets of prototype observation data of branch river sections of Yichang-Jiujiang midstream in 2003-2015, the empirical relations of n-Fr are obtained respectively as follows:
calculating n value of branched river branch segment by using n-Fr empirical relation, comparing n measured value with n measured value, respectively substituting n measured value and calculated value into
The actual measurement value and the estimated value of the resistance coefficient λ are calculated, and the result is plotted in fig. 8, where (a) in fig. 8 is a graph of the calculated value of n and compared with the actual measurement value of n, and (b) in fig. 8 is a graph of the calculated value of the resistance coefficient λ and compared with the actual measurement value of n, and the degree of coincidence between the calculated value of the formula and the actual measurement value is evaluated by using statistical parameters such as root mean square RMS, geometric standard deviation GSD, root mean square error RMSE, and the like. The result shows that the n-Fr relational expression established based on the actual measurement data of the branched river section can basically reflect the change rule of the resistance of the branched river section along with the water flow strength, and meanwhile, the fact that other factors influencing the resistance of the branched river section are not considered is also found, the degree of deviation of the calculation result is relatively large, and the calculation accuracy needs to be further improved.
On the basis of the empirical relation between n and Fr, factors reflecting the roughness of the bed surface, the cross section shape and the reduction and expansion of the cross section of the branched section are further added, and a general type of the following branched section mangning roughness coefficient calculation formula is constructed:
wherein a, b, c, d and e are empirical coefficients.
Substituting the same prototype observation data into the formula to obtain the following empirical formula of branched river reach Manning roughness coefficient:
calculating n value of the branched river section of the middle branch of Yangtze river by using the empirical formula, and substituting the calculated n value into the
Calculating the calculated value of the resistance coefficient lambda, comparing the calculated values of n and lambda with the measured values respectively, and plotting the result as shown in fig. 9, (a) in fig. 9 is the calculated value of n and is compared with the measured value of n, and (b) in fig. 9 is the calculated value of the resistance coefficient lambda and is compared with the measured value, the used measured data is consistent with the data of the empirical formula for calibrating the Manning roughness coefficient, and the conformity degree of the calculated value of the formula and the measured value is evaluated by using statistical parameters such as root mean square RMS, geometric standard deviation GSD and root mean square error RMSE. In general, the formula can better reflect the comprehensive effect that different factors influence the branched river section resistance, and the calculation accuracy is higher.
As shown in fig. 10 and 11, they correspond to the single section and the branched section of the embodiment of the present invention, respectively, the calculated value of the resistance coefficient obtained by the integrated resistance coefficient formula of the branched river section according to 2016-2019 68 sets of prototype observed data and 159 sets of physical model test measured data is compared with the measured value, and other measured data except the calibration parameter is used, fig. 10 (a) is the calculated value of the single section n and is compared with the measured value n, and fig. 10 (b) is the calculated value of the single section resistance coefficient λ and the measured value comparison graph; fig. 11 (a) is a comparison graph between the calculated value of the cross section n of the branch and the measured value of n, and fig. 11 (b) is a comparison graph between the calculated value of the resistance coefficient λ of the cross section of the branch and the measured value.
Referring to fig. 12, in the embodiment of the present invention, a pacific waterway is selected as a typical river reach, and a mathematical model is established, as shown in fig. 13. The Taiping mouth water course is arranged above a Chenjiawan and is arranged below the jade and the terrace, and the total length is about 18km. The left side of a river section inlet is provided with depression and river inlet branches, the right side of the river section inlet is provided with a flattening port for splitting, and the river section inlet can be divided into a flattening port straight branch and a three-eight-beach slightly-bent branch from top to bottom according to different plane appearances. And covering the verification river reach with a 220 multiplied by 100 conformable orthogonal curve grid, wherein the grid interval in the water flow direction is 66-115 m, and the grid interval in the vertical water flow direction is 15-30 m.
In order to compare the calculation effects of the Manning roughness coefficient empirical formula under different flow conditions, the method collects three river channel topographic maps, actually measured hydrological cross section flow velocity and water level measurement data of 2014.12, 2015.08 and 2018.08 at different times. The import respectively gives three-level flow of withered, medium and flood(7020 m each) 3 /s、17350m 3 /s、27500m 3 /s) as an upper boundary condition for the model; the outlet water level is obtained by interpolation according to the actual measured water level data of the upstream and the downstream.
Trial calculation is needed when the roughness is determined by utilizing the Manning roughness coefficient empirical formula established by the invention in the mathematical model, and the trial calculation steps are as follows:
(1) at the beginning of the calculation, a uniform initial roughness value n = n is given to the entire calculation range 0 Solving initial flow field distribution and river channel section geometry (A, B, U, A/A0 and the like) and substituting the initial flow field distribution and the river channel section geometry into the right side of the branch river section comprehensive resistance coefficient empirical formula to obtain a calculated value n of roughness;
(2) comparing n and n, if the difference between n and n is larger, updating n according to the principle of successive approximation based on the difference between n and n, and substituting the updated n into the model for recalculation;
(3) and substituting the calculation result of the model into the right side of the comprehensive resistance coefficient formula to solve n, comparing the calculated result with the updated n, repeating for many times until the difference between n and the updated n is within a certain error range, namely, considering that n is updated to a real roughness value, and completing the solution of the model roughness.
The calculation flow chart is shown in fig. 14.
Let iterative calculation error control value e =0.05, after calculating the roughness of the three measurements by the above method, output the final cross-section water passing area, river width, cross-section average flow velocity and cross-section average water level calculation values (denoted as a, B, U and H, respectively) and compare them with the measured values (a ', B', U 'and H'), the result is shown in fig. 15, where (a) is the cross-section average water level calculation value and measured value, (B) is the cross-section average flow velocity calculation value and measured value, (c) is the water passing area calculation value and measured value, and (B) is the error range of each variable of the river width calculation value and measured value, see table 1.
Comparative example
In the mathematical model, the roughness determined by the measured data can also describe the river resistance under the verification condition more accurately, but the roughness determined by the formula method can not be better made up for the deficiency because the automatic adjustment can not be realized according to the change of the riverbed erosion and water flow conditions in the calculation process.
The river course roughness under the terrain condition is determined by actually measuring the water level and the flow rate data rate through 2014.12. And (3) roughness rating is performed in a segmented manner, namely, a plurality of roughness intervals are divided along the way, after uniform roughness values are given to all the intervals, a water surface line along the way is solved by using a mathematical model, the calculated water level and the measured water level of each measured hydrological section (the position is shown in figure 12) are compared, the value of the roughness is adjusted according to the deviation of the calculated water level and the measured water level until the difference value between the calculated water level and the measured water level is controlled within +/-5 cm, and the roughness rated according to the ratio can reflect the real river resistance.
And (3) endowing the roughness value determined by the ratio to a model to respectively calculate 2015.08 and 2018.08 flow velocity distribution under the topographic condition, and comparing the flow velocity distribution with the calculation result of roughness determined by the resistance formula method in the previous section.
Fig. 16 shows comparison of course water lines for the respective calculation conditions, in which fig. 16 (a) is a comparison graph of 12 months in 2014, fig. 16 (b) is a comparison graph of 08 months in 2015, and fig. 16 (c) is a comparison graph of 08 months in 2018. Tables 1 and 2 further show the error ranges and average deviations of the variables (cross-sectional flow area a, river width B, cross-sectional average flow velocity U, and cross-sectional average water level H) as represented by the statistic Re = (∑ (Mi-Ni) 2/N) 1/2 (where i represents the number of data, and M and N represent calculated and measured values, respectively).
Obviously, because the river channel resistance is correspondingly adjusted along with the change of the riverbed erosion and deposition and the water flow conditions, the change characteristic of the river channel resistance cannot be reflected by adopting the traditional method for measuring the roughness by actually measuring data. When the branch river segment Manning roughness coefficient empirical formula established by the invention is applied to a mathematical model, the roughness value can be automatically adjusted according to the riverbed erosion and silt adjustment and the change of the inlet flow, so that the roughness determination and the solution of the flow field are interactively carried out, the complicated actually-measured data calibration process is avoided, the dynamic adjustment condition of the river channel resistance along with the change of the water flow and the river channel boundary condition can be reflected, and the simulation precision of the mathematical model is improved.
TABLE 1 calculation error Range of variables
TABLE 2 mean deviation of variables
The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications, additions and substitutions for the specific embodiments described may occur to those skilled in the art without departing from the spirit of the invention or exceeding the scope of the invention as defined in the accompanying claims.
Claims (7)
1. A branched river segment Mannich roughness coefficient characterization method is characterized by comprising the following steps:
s1, selecting a Freund number Fr to reflect the water flow strength;
s2, selecting relative water depth to reflect the roughness of the bed surface;
s3, selecting a section river phase coefficient to reflect the cross section form;
s4, aiming at the influence of the contraction and expansion of the section of the branch section on the resistance, the water passing area A of the section of the branch section and the water passing area A of the single section of the upstream are used 0 The ratio is used as a parameter for reflecting the reduction and expansion degree of the section of the branch section;
s5, establishing an empirical relation between n and Fr, wherein n is a Mannich roughness coefficient;
s6, further adding factors reflecting the roughness of the bed surface, the cross section form and the section shrinkage and expansion degree of the branched section on the basis of the empirical relation of n-Fr in the step S5, and constructing a general type of a branched section mangning coefficient calculation formula
Wherein a, b, c, d and e are empirical coefficients, and H is the average depth of section,D 50 Is the median diameter of bed sand, epsilon is the cross-section river phase coefficient, A is the water passing area of the branch section, A 0 The water passing area of the upstream single section is obtained;
and S7, substituting the prototype observation data into the formula, and calibrating to obtain empirical coefficients a, b, c, d and e, thereby finally obtaining the Manning roughness coefficient empirical formula.
2. The branched river section Mannich roughness coefficient characterization method according to claim 1, characterized in that: in step S2, the expression of the relative water depth is H/D 50 The larger the H/D50, the smaller the bed surface roughness.
3. The method for characterizing branched river segment Mannich roughness coefficient according to claim 1, wherein: in step S3, a section river facies coefficient epsilon = B is selected 1/2 H, river phase coefficient epsilon' = B substituted into maximum water depth of section 1/2 /h max And H/H max Three parameters are analyzed to be related to n, and three cross section shape parameters have certain influence on n along with epsilon, epsilon' and H/H max In addition, n tends to decrease, i.e., the resistance of the wide and shallow branch section is smaller than that of the narrow and deep branch section, but of the three morphological parameters, the correlation between epsilon and n is the best, epsilon' is the second, the relationship between n and H/hmax is relatively scattered, and the correlation is the worst, so that the cross-sectional river facies coefficient is selected to reflect the cross-sectional morphology.
4. The method for characterizing branched river segment Mannich roughness coefficient according to claim 1, wherein: in step S4, the water passing area a of the branched section and the water passing area a of the single section of the upstream section are divided 0 The ratio is expressed as A/A 0 。
5. The method for characterizing branched river segment Mannich roughness coefficient according to claim 1, wherein: in the step S5, the Manning roughness coefficient n and Fr present a better power function relationship,
the basic form of the relation from n to Fr is proposed by taking n as a dependent variable and Fr as an independent variable:
n＝aFr b 。
6. a branched river section river channel resistance coefficient calculation method based on a Manning roughness coefficient is characterized by comprising the following steps: the method comprises the following steps:
step I, according to the branched river reach Manning roughness coefficient characterization method of any one of claims 1 to 5, calculating to obtain an empirical formula of the research river reach Manning roughness coefficient;
and II, calculating according to an empirical formula of the Manning roughness coefficient to obtain the integrated resistance coefficient of the branched river section.
7. The method for calculating the integrated branch river section resistance coefficient based on the Manning roughness coefficient as claimed in claim 6, wherein: in the step II, the Mannich roughness coefficient is substituted into
Calculating a drag coefficient λ, where U represents the average flow velocity, U * The friction flow rate, the metabolic coefficient, the gravitational acceleration and the hydraulic radius are respectively expressed by C, g and R.
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| CN115982917A (en) * | 2023-03-20 | 2023-04-18 | 长江水利委员会长江科学院 | Plain river low water level bayonet identification method, system and medium |
| CN116202483A (en) * | 2023-03-04 | 2023-06-02 | 北京七兆科技有限公司 | Method, device, equipment and medium for determining water level and flow relation of river section |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116202483A (en) * | 2023-03-04 | 2023-06-02 | 北京七兆科技有限公司 | Method, device, equipment and medium for determining water level and flow relation of river section |
| CN116202483B (en) * | 2023-03-04 | 2024-03-19 | 北京七兆科技有限公司 | Method, device, equipment and medium for determining water level and flow relation of river section |
| CN115982917A (en) * | 2023-03-20 | 2023-04-18 | 长江水利委员会长江科学院 | Plain river low water level bayonet identification method, system and medium |
| CN115982917B (en) * | 2023-03-20 | 2023-06-23 | 长江水利委员会长江科学院 | Method, system and medium for identifying plains river withered water level bayonet |
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